China Communications Construction Company complete highway tunnel connecting Lhasa with Zhanang county in the Tibet autonomous region on Wednesday after 7 years of construction. High altitude, less oxygen, cold, length and difficult geology took 7 years instead of normal 4.

It is world's highest altitude tunnel (at entrance 4,248 meters; at exit 4,117 meters above sea)

https://www.chinadaily.com.cn/a/202306/28/WS649c2c8da310bf8a75d6c26c.html